See the OTHER posted discussion started by someone else earlier today where the exact same question was asked with respect to shutting down the v2.x firmware single bay My Cloud units.
https://community.wd.com/t/how-to-shutdown-mycloud-single-3tb/207642
Yes one can use SSH but the commands may be slightly different between the first generation v4.x My Cloud and the second generation v2.x My Cloud. Use the forum search feature and search for Shutdown to find the various prior discussions on how to use SSH to shut down a v2.x firmware My Cloud.
If one performs a 4 second reset or 40 second reset after a firmware upgrade they should not loose any use data. See the following WD Support Document for more information on what Dashboard settings/values are reset with a 4 second or 40 second reset.
